Additive for production of spheroidal graphite cast iron consisting mostly of calcium-silicon



United States Patent 3,415,642 ADDITIVE FOR PRODUCTION OF SPHEROIDAL GRAPHITE CAST IRON CONSISTING MOSTLY OF CALCIUM-SILICON Hiroshi Matsumoto, Yono, Japan, assignor to Tokyo Kakin Kogyo (10., Ltd., Tokyo, Japan No Drawing. Filed Apr. 4, 1966, Ser. No. 539,624 Claims priority, application Japan, Dec. 13, 1965, 40/ 76,207 2 Claims. (Cl. 75-130) This invention relates to an additive for production of cast iron containing spheroidal graphite, more particularly an additive consisting mostly of calcium-silicon for production of cast iron containing spheroidal graphite on a large scale at a low cost, which is prepared by coating said calcium-silicon with a solution of subcomponent comprising calcium chloride or a mixture of calcium chloride and a chloride or rare earth element, said solution further containing at least one of auxiliary compound selected from the group consisting of magnesium chloride, barium chloride, oxides of rare earth elements, fluorides of rare earth elements, carbonates of rare earth elements, magnesium fluoride, barium carbonate, and the like, and then by dehydrating thus coated calcium-silicon. Cast iron containing spheroidal graphite can be produced easily at a high yield by adding said additive to the surface of molten pig iron or by penetrating it under pressure into a molten bath.

The reasons for adding such compounds as mentioned above to calcium-silicon are as follows:

(1) Calcium chloride, chlorides of rare earth elements, magnesium chloride, and barium chloride are all soluble in water to produce an aqueous solution thereof, of which an aqueous solution of calcium chloride and/or chlorides of rare earth elements is not crystallized even when heated to evaporate the moisture thereof but become a highly viscous solution, and such a viscous solution is solidified upon cooling. It is possible to disperse magnesium chloride and barium chloride in the viscous solution. If powder particles of calcium-silicon are added to such a highly viscous solution containing magnesium chloride and/ or barium chloride and the solution is stirred while heating for dehydration, the calcium chloride and/or chlorides of rare earth elements in the solution is solidified to form shells containing magnesium chloride and/ or barium chloride to coat the surface of each powder particle of calcium-silicon.

(2) Any of said four kinds of compounds can be obtained easily at a low cost.

(3) Calcium chloride has a low melting point (773 C.) while having a comparatively high boiling point (over 1,600 C.), and hence liquid state calcium chloride has a high fluidity and acts to reduce the melting point of other metal oxides and increase the fluidity of such metal oxidesQIf such calcium chloride is added to the molten bath of pig iron, it acts to reduce the melting points of metal oxides, metal sulfides, and other impurities therein, and improves the fluidities thereof, thereby the removal of impurities comprising such oxides and sulfides can be made considerably easier, and resulted in a clean bath substantially free from the dross of iron..

On the other hand, calcium chloride contained in the coating layer tightly adhered to the outer surface of each calcium-silicon particle acts to prevent the chemical reaction of the calcium with oxygen or carbon on the surface of or inside of the molten bath when the additive is added thereto, and accordingly wasteful consumption of calcium is prevented and the quantity of calciumsilicon additives necessary for the production of spheroidal graphite can be minimized.

(4) Chlorides of rare earth elements, magnesium chlo- 'ice ride and barium chloride cause following chemical reactions upon adding them to a molten bath together with the calcium-silicon additive.

The CaCl thus produced acts in the molten bath as described in the preceding paragraph 3, and R (rare earth element) thus isolated acts to facilitate the production of spheroidal graphite in the molten bath, while Ba element thus isolated acts to make the size of spheroidal graphite particles uniform and to facilitate the production of ferrite.

(5) Finely powdered water insoluble auxiliary agents, such as oxides carbonates and fluorides of rare earth elements, magnesium fluoride, barium carbonate, etc., are dispersed and suspended uniformly in the liquid state calcium chloride to adhere and coat the outer surface of each calcium-silicon particle. Accordingly, there is no danger of segregation, which sometimes happens in the case of alloys, and hence uniform composition can be always obtained easily.

(6) Auxiliary agents contained in the calcium chloride coating of each calcium-silicon particle, such as oxides, carbonates and fluorides of rare earth elements, magnesium fluoride, and barium carbonate, cause following chemical reactions upon adding them to a molten bath together with the calcium-silicon additive.

The CaO and CaF thus produced are removed from the molten bath due to the fact that calcium chloride in the molten bath acts to reduce the melting point thereof and at the same time increase the fluidity thereof. The rare earth element R and Mg element act as simple substances respectively to facilitate the production of spheroidal graphite while Ba acts to make the size of spheroidal graphite particles uniform and to facilitate the production of ferrite.

(7) The dehydration process of calcium chloride can be carried out with comparative ease by heating. Magnesium chloride and chlorides of rare earth elements, which are normally difficult to dehydrate, can be easily dehydrated by using ammonium chloride.

By the reason set forth as above essential coating materials of calcium-silicon of the invention are selected to be calcium chloride and chlorides of rare earth elements.

The composition of the additives of the invention consists of 20 to 96% by weight of Ca--Si, 2 to 60% by weight of CaCl or mixture of CaCl and R01 and 2 to 40% of at least one compound selected from the group consisting of MgCl BaCl BaCO R 0 R (CO RF3 and MgF If the contact of CaCl or the mixture of CaCl and RG1 is less than 2% or CaSi content is more than 96% in the additives of the invention, sufiicient coating can not be attained. On the other hand, if the content of CaCl or the mixture of CaCl and RG1 is more than 60% or CaAi content is less than 20% in the additives of the invention a great quantity of slugs is produced due to excessive amount of the coating agent.

If the content of the auxiliary agent such as MgCl 3 B3012, MgFz, R303, R2(CO3)3, RF3 and BaCO iS less than 2%, the eifects of the auxiliary agents can not be attained. On the other hand, if the content of said auxiliary agents is more than 40% in the additives of the in Example 1 A mixture which consists of 10 kg. of hydrous chloride of rare earth elements, 5 kg. of calcium chloride, 5 kg. of hydrous magnesium chloride, and 1 kg. of barium chlovention when the additive contains the lowest content of 5 ride was taken in a vessel and melted b heatin the -C2I S1 t-hen It bei-iomes lmposslbl-e-to reduce chem vessel. After the mixture melted completZly, 2 k g. of many the enme quanmy of i auxlhary agents thus ammonium chloride was added thereto then the conig g g g g gg sg i zfig g gz zg' the invem tents poured out on a drying pan made of iron plate. tion determinld as described above Thereafter, 40 kg. of pulverized calcium-silicon of under If the aforementioned additive of the invention is added zpgigihg i gggi g gg gif gf sg zgg g gg to a molten bath of hyper-6112mm i (contalmfig gradually and make adhere chlorides of rare earth elea st iicfn go fa ii g 2 5 t?) 322 if C ai ic l 12 2 2 5 21? merits, calcium chlorides and magnesium chloride on the a t f c I I t. r .11 S1), then cast iron containing spheroidal graphite, which 15 gt gg gg g gg g i i fi gg 252 has a chemical compo sltion of less than 002% of cerium white smoke of ammonium chloride rose from the said .02 of gg s fi g gg f g gfi and less than 0 contents. The drying and dehydrating treatment was car- The salient features of the additive of the invention are 2 :3 g i g g ggg g gg 223 32 2; 5 3 353 :3 55? o 53 additive of the invention is very easily melted sealed vessel and after cooled replaced the contents in a to the molten bath. Since the chemicalreaction of such :ealed ag lmlyefhylme bag and Stored salts as RG1 MgCl MgF BaQl in the additive of the 3 1: t; l l d 1 lf f K h d H invention with Ca are exothermic, there W111 be no temgg 53 2 g in 222i illi ec l ig g gai ig a? f g fiz z? h e il g g iig g gi a graphite crucible by using a Kryptol electric furnace, molten bath is sometimes increased by the addition of said and then the above descnbed addltlve of the lnventlon additive. Furthermore the aforementioned exothermlc regi h gv i igz 1 12 t tl fg t a cg se f zgrgg t sg ge gi actions following the addition of the additive of the ina e 9 Q Vention are very mild and there will he no danger of cansadd1ng O.5% of ferro-silicon as an moculant, but not inocin-g explosive reactions as those reactions following an 111 gifefl g g other EZLPI E i-j d to 1 ran f addition of metallic magnesium. m Was 0 e In a P 11 y 0 (b) The composition of the additive of the invention test pieces consisting of rods of 20 mm. diameter by using can be made uniform according to the aforementioned green Sand molds 9 carry P mlcroscopic analysis 011 a process, and there is no danger of resulting from segregairaftllre 1 g 126st p 1e;1:e.dThe 1results of the chemtion, WhlCh 1S sometimescaused In the case of alloys. The al'la Y of t amals 1 e P Iron and Sald auxiliary agents in the invention are tightly adhered to rfllcroscoplc vanalysls are shown In Tables 1 and 2 P the outer surface of each CaSi particle, and hence they Y- react quickly without any loss.

(c) The chance of producing cementite is greatly re- 40 TABLE 1 duced by using the additive of the invention, and hence mements C Si Mn P 5 Fe thin or small cast articles can be produced without any t t t 8. 1. .2 2 further treatment if cast ll'OIl is prepared with the addltive Con en (percen 96 87 0 6 0 07 0 026 Rest TABLE 2 Additive Inoculant Sample No. of the charge Type of graphite in the Com position invention (percent) cast iron (percent) (percent) (percent) 02-201 3 None spheroidal graphite, 100 Ferrite, 70. 0Z-202 2 Fe-Si, 0.5 do Ferrite, 60. 0Z203 1. 5 Fe-Si, 0.5 spheroidal graphite, 80 Do. 0Z204 1 Fe-Si, 0.5- spheroidal graphite, 70 Ferrite, 70. 0.5 Fe-Si, 0.5-.. Graphite flake Ferrite, 90.

of the invention. Cast iron articles of high mechanical Example 2 strength can be obtained without any further treatment,

since a large degree of graphitization is attained by using the additive of the invention. The composition of cast iron produced by using the additive of the invention is mostly of ferrite type, and provided with a high tensile strength. The tensile strength of said cast iron is to kg./mm. without applying any further treatments and the corresponding elongation is 4 to 18% (d) The number of shrinkage defects in the cast article is also minimized, thereby the size of the riser can be made smaller compared with that of conventional cast iron. Thus, the iron casting design can be considerably simplified.

(e) Practically no dross is produced, and the slugs can be also easily removed after being processed.

(f) Responsive to the size, thickness, and use of the article to be cast, the ratio between the quantities of calcium-silicon and the auxiliary agents in the additive of the invention can "be easily modified to meet the specific needs of each cast article.

The invention will now be described in further detail by taking examples.

A solution was prepared by dissolving 7.5 kg. of hydrous calcium chloride in 3 l. of water by heating. Then, 1 kg. of ammonium chloride, 7.5 kg. of fluorides of rare earth elements, 5 kg. of magnesium fluoride, and 1 kg. of barium carbonate were added to said solution and stirred to mix thoroughly. After the solution was poured on a drying pan made of iron, 35 kg. of pulverized calciumsilicon of under 3 mm. diameter were added, then the drying pan was heated and dried by applying a flame directly thereto in order dehydrate gradually the calcium chloride and make adhere tightly the calcium chloride withchloride of rare earth elements, magnesium fluoride and barium carbonate onto the outer surface of each calcium-silicon particle therein.

When the contents was heated to 560 C., white smoke of ammonium chloride rose therefrom. The drying and dehydrating treatment was carried out continuously until said white smoke Was ceased, and then the pan with the contents in it was cooled in a sealed vessel and after cooled replaced the contents in a sealed container such as a polyethylene bag, and stored to use as the additive of the invention.

On the other hand, 1 kg. of Kamaishi ductile pig iron formly in the solution of calcium chloride and tightly ad- C having a composition as shown in Table 1 was melted here to the outer surface of each calcium-silicon particle in a graphite crucible by using a Kryptol electric furnace, when dehydrated by heating and also contact and react and then the above described additive of the invention with calcium when mixed with a molten bath of cast was added to the surface of the molten bath. The molten 5 iron, thereby the desired cast iron can be produced at a bath was inoculated in the case of some test pieces by high yield even when only small quantity of the additive adding 0.5% of ferro-silicon as an inoculant, but not inocof the invention is applied thereto. ulated in the case of other test pieces. The molten bath Since the additives of the invention are hygroscopic, was then molded into a plurality of test pieces consisting immediately after dehydration drying it is preferable to of rods of 20 mm. diameter by using green sand molds 10 store them in moisture-proof containers such as polyethylto carry out microscopic analysis on a fracture of each one bags, or to store them by applying a small quantity said test piece. The results are shown in Table 3. of non-drying oil on the surface of the additives.

TABLE 3 Additive Inoculant Sample No. of the charge Type of graphite in the Composition invention (percent) cast iron (percent) (percent) (percent) 0Z-256 3 None spheroidal graphite, 100.-.. Ferrite, 60.

0Z-257 2 Fe'Si, 0.5 do Ferrite, 70.

0Z-258 1. 0 Fe-Si, 0.5... spheroidal graphite, 80 D0.

0Z-259 0.5 Fe-Si, 0.5. spheroidal graphite, 40... Ferrite, 80.

The aforementioned test pieces of mm. diameter WhatIclaim is: were then shaped into tensile test pieces of 14 mm. di- 1. An additive for production of cast iron containing ameter to carry out tensile tests. The tensile strength of spheroidal graphite, consisting of 20 to 90% by weight of test pieces containing not less than 80% of spheroidal calcium-silicon as amain component, 2 to 60% by weight graphite was 45 to 60 kg./mm. and the corresponding of at least one sub-component selected from the group elongation proved to b 3 to 12%. consisting of calcium chloride and a mixture of calcium It has been proved in the above examples that the adchloride and at least one of chlorides of rare earth eleditives of the invention consisting mostly of calciummerits, and 2 to 40% by weight of at least one auxiliary silicon particles coated with calcium chloride or with a mpound Se ected from the group consisting of magmixture of calcium chloride and one or more of chlorides nesillm chloride, barium chloride, oxides of rare earth of rare earth elements, said coating being provided with ments, fluorides of rare earth elements, carbonates of rare auxiliary agents such as magnesium chloride, barium earth elements, magnesium fluoride and barium carbonate.

2. An additive according to claim 1, wherein said calcium-silicon comprises a plurality of small particles, each said particle is coated with a layer of said sub-component that such an additive is ready to make chemical reactions auxlhaflry compound sald layer bemg PrePfred by upon adding it into a molten bath to prevent with the plymg a hlghly fi fi condensed solution sub-component mixed with at least one of said auxiliary aid of said calcium chloride the bondage of the calcium in said additive with oxygen and carbon so that wasteful g f g g then by dehydrating and drymg thus consumption of the additive may be prevented, that cal cium chloride in the additive reduces the melting points References Clted of other metal oxide and others and improves the fluidity UNITED STATES PATENTS chloride, magnesium fluoride, barium carbonate, etc., dispersed uniformly in said coating, is effective to produce 35 spheroidal graphite in cast iron. Besides it has been proved thereof in order to remove completely impurities in the 4 ,821,473 1/1958 Moore 75130 cast iron from the molten bath, thereby the content of 97 /19 7 Kusaka 75130 the dross 1n the cast 1IOI1 can be considerably reduced. L DEW AYNE RUTLEDGE Primary Examiner- It has been also proved that such water insoluble auxiliary agents also as fluorides and/or carbonates of THOMAS D-PENDER,AS-Yismm Examinerrare earth elements and/or magnesium fluoride, and/or us CL barium carbonate, etc., are dispersed and suspended uni- -58 

1. ADDITIVE FOR PRODUCTION OF CAST IRON CONTAINING SPHEROIDS GRAPHITE, CONSISTING OF 20 TO 90% BY WEIGHT OF CALCIUM-SILICON AS A MAIN COMPONENT, 2 TO 60% BY WEIGHT OF AT LEAST ONE SUB-COMPONENT SELECTED FROM THE GROUP CONSISTING OF CALCIUM CHLORIDE AND A MIXTURE OF CALCIUM CHLORIDE AND AT LEAST ONE OF CHLORIDES OF RARE EARTH ELEMENTS AND 2 TO 40% BY WEIGHT OF AT LEAST ONE AUXILIARY COMPOUND SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM CHLORIDE, BARIUM CHLORIDE, OXIDES OF RARE EARTH ELEMENTS, FLUORIDES OF RARE EARTH ELEMENTS, CARBONATES OF RARE EARTH ELEMENTS, MEGNESIUM FLUOURIDE AND BARIUM CARBONATE. 